Portal braking system

ABSTRACT

A braking system for a portal lift assembly includes a shaft operably connected to a vehicle power source and effective to directly or indirectly rotate a wheel of the vehicle upon rotation of the shaft about its axis, a piston positioned along the shaft and effective for applying an axial force along the axis of the shaft, a fluid channel fillable with a non-compressible fluid and effective to apply a hydraulic force to the piston when pressure is applied to fluid in the line, a pressure plate positioned along the shaft and effective for applying an axial force along the axis of the shaft in response to the application of an axial force by the piston. A clutch pack is positioned between the pressure plate and the piston, and includes two sets of clutch plates radially surrounding the shaft. The first set of clutch plates is connected to the shaft in a manner effective to cause those clutch plates to rotate about the axis of the shaft when the shaft rotates. The second set of clutch plates is prevented from rotating about the axis of the shaft. Members of the first set of clutch plates are interspersed between members of the second set of clutch plates, so that when the clutch pack is sufficiently compressed by axial forces applied by the piston and the pressure plate, the first set of clutch plates is forced against the second set of clutch plates so that friction forces between members of the first set of clutch plates and members of the second set of clutch plates slow and may subsequently stop the rotation of the shaft.

REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 62/809,154, filed Feb. 22, 2019, the entirecontents of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to portal wheel ends for liftingthe wheels of an off road vehicle such as an all-terrain vehicle (ATV)or a utility task vehicle (UTV), and more particularly to a brakeassembly for improving the braking power and reliability of suchassemblies.

BACKGROUND OF THE INVENTION

Portal boxes are known to ATV and UTV enthusiasts for providingincreased ground clearance, or lift, and the low gearing needed forbigger tires. Such boxes are typically mounted to an ATV/UTV by firstmounting a backing plate to the suspension of the vehicle, and by thenmounting the portal box to the backing plate. U.S. Pat. No. 8,985,264 toShirley is one example of such a device.

Among the improvements made by applicant to portal gear box assembliesare improvements designed to lengthen the wheelbase of the vehicle andto provide the ability to select among several wheelbase lengths. Theconnection between the portal output shaft and the associated wheel hubhas also been improved by applicant to reduce vibration in the wheel.

The braking system used by portal gear boxes has not heretofore beenoptimized to improve braking power and reliability. The presentinvention addresses that need.

SUMMARY OF THE INVENTION

Briefly describing one aspect of the present invention, there isprovided a braking system for a portal lift assembly. The inventivebraking system includes a portal box with an input for receiving a stockaxle, a linking mechanism for connecting the stock axle to an outputshaft, an output shaft extending outward from the portal box andconnected to the stock axle through the linking mechanism, a pistonadjacent one portion of the output shaft and driven by brake fluid in abrake line, a pressure plate adjacent another portion of the outputshaft and effective for resisting an axial force applied by the piston,and a clutch pack disposed between the piston and the pressure plate.

The clutch pack comprises a first set of clutch plates radiallysurrounding a portion of the output shaft, and a second set of clutchplates also radially surrounding a portion of the output shaft. Thefirst set of clutch plates is connected to the output shaft in a mannereffective to cause those plates to rotate about the axis of the shaftwhen the output shaft rotates, and the second set of clutch plates isconnected to the portal box housing in a manner effective to prevent thesecond set of clutch plates from rotating with respect to the shaft.Members of the first set of clutch plates are interspersed betweenmembers of the second set of clutch plates, so that when the clutch packis sufficiently compressed by axial force applied by the piston and thepressure plate, the first set of clutch plates is forced against thesecond set of clutch plates so that frictional forces between the twosets of plates cause the first set of plates to slow and ultimatelystop.

The piston is driven by brake fluid in a brake line. When pressure isapplied to the fluid in the brake line, the piston is moved against theclutch pack toward the pressure plate, thereby compressing the clutchpack and forcing the first set of clutch plates against the second setof clutch plates with a force effective to restrict or prevent themovement of the first set of clutch plates with respect to the secondset of pressure plates. Since the second set of clutch plates isprevented from rotating with the shaft, this action applies a brakingforce to the vehicle.

A wheel hub may be mounted to the distal end portion of the outputshaft, and is adapted to turn a wheel mounted to the hub upon rotationof the output shaft.

A second aspect of the present invention provides a braking system for avehicle. As in the first embodiment, the system comprises a shaft, apiston driven by a fluid in a fluid channel, a pressure plate, and aclutch pack. The shaft is operably connected to a vehicle engine, and iseffective to directly or indirectly rotate a wheel of the vehicle uponrotation of the shaft. The piston is positioned at a first positionalong or around the shaft, and is effective for applying an axial forcein a first direction along the axis of the shaft. The piston may bemoved axially along the shaft when pressure is applied to the piston bya fluid in a fluid channel, such as brake fluid in a brake line. Thepressure plate is positioned at a second position along or around theshaft, and is effective for applying an axial force in a seconddirection opposite the first direction along the axis of the shaft inresponse to the application of an axial force in the first direction bythe piston.

The clutch pack is positioned between the pressure plate and the piston,and comprises a first set of clutch plates radially surrounding aportion of the shaft, and a second set of clutch plates radiallysurrounding a portion of the shaft. The first set of clutch plates isoperably connectable to the shaft in a manner effective to cause thoseclutch plates to rotate about the axis of the shaft when the shaftrotates, and the second set of clutch plates is prevented from rotatingabout the axis of the shaft. Members of the first set of clutch platesare interspersed between members of the second set of clutch plates, sothat when the clutch pack is sufficiently compressed by axial forcesapplied by the piston and the pressure plate, the first set of clutchplates is forced against the second set of clutch plates so that the twosets of clutch plates must move together or not at all. When the pistonis moved against the clutch pack toward the pressure plate, the clutchpack is compressed, thereby forcing the first set of clutch platesagainst the second set of clutch plates with a force effective torestrict or prevent the movement of the first set of clutch plates withrespect to the second set of pressure plates, and thereby applying abraking force to the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the braking system ofthe present invention, in partial section.

FIG. 2 is an elevational sectional view of one embodiment of the brakingsystem of the present invention.

FIG. 3 is a schematic exploded view of one embodiment of the brakingsystem of the present invention.

FIG. 4 is a perspective view of the housing, input gear, output gear,output shaft, pressure plate, clutch pack, and piston of one embodimentof the present invention, in partial section.

FIG. 5 is a perspective view of the outer housing cover, output gear,output shaft, and clutch pack of one embodiment of the braking system ofthe present invention, in partial section.

FIG. 6 is a perspective view of the housing, output shaft, and clutchpack of one embodiment of the present invention, in partial section.

FIG. 7 is a plan view of one of a first set of clutch plates from aclutch pack used in certain embodiments of the present invention.

FIG. 8 is a plan view of one of a second set of clutch plates from aclutch pack used in certain embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to certain embodiments andspecific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the described device, and such further applications ofthe principles of the invention as illustrated therein, beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

In one embodiment the inventive braking system comprises: a) a shaft,operably connected to a vehicle power source and effective to directlyor indirectly rotate a wheel of the vehicle upon rotation of the shaft;b) a piston, positioned at a first position along or around the shaftand effective for applying an axial force in a first direction along theaxis of the shaft; c) a pressure plate, positioned at a second positionalong or around the shaft and effective for applying an axial force in asecond direction opposite said first direction along the axis of theshaft in response to the application of an axial force in the firstdirection by the piston; and d) a clutch pack, positioned between thepressure plate and the piston, the clutch pack comprising a first set ofclutch plates radially surrounding a portion of the shaft, and a secondset of clutch plates radially surrounding a portion of the shaft. Thesystem also preferably comprises a brake line effective to apply a forceto the piston.

The first set of clutch plates is connected to the shaft in a mannereffective to cause those clutch plates to rotate about the axis of theshaft when the shaft rotates, and the second set of clutch plates isconnected to the vehicle in a manner effective to prevent those platesfrom rotating about the axis of the shaft. Members of the first set ofclutch plates are interspersed between members of the second set ofclutch plates, so that when the clutch pack is sufficiently compressedby axial forces applied by the piston and the pressure plate, the firstset of clutch plates is forced against the second set of clutch platesso that the two sets of clutch plates must move together or not at all.

Accordingly, when a force is applied to the fluid in the brake line, thepiston is moved against the clutch pack toward the pressure plate,thereby compressing the clutch pack and forcing the first set of clutchplates against the second set of clutch plates with a force effective torestrict or prevent the movement of the first set of clutch plates withrespect to the second set of pressure plates, and thereby applying abraking force to the vehicle.

More particularly describing various elements and features of thisembodiment of the inventive braking system, the invention is intendedfor use with vehicles that ride on wheels or tracks driven by an axlepowered by an engine or other power source, such as a battery. Forexample, the inventive braking system finds particular utility onall-terrain vehicles and utility task vehicles, such as the ATVs andUTVs offered by Polaris, Can-Am, Yamaha, Kawasaki, Arctic Cat, Honda,and the like. These vehicles require superior braking and are frequentlysubjected to increased stress and torque when compared to lighter-dutyvehicles.

As is conventional in the art, the vehicle has an axle that rotatesaround an axis to turn the wheels or tracks or otherwise to power thevehicle. In the most preferred embodiments, the axle is made of heavyduty steel or a steel alloy, such as heavy-duty 4340 chromoly steel.

The inventive braking system uses a hydraulically-activated clutch packto slow the axle and stop the axle from rotating. The clutch pack ispositioned between a piston and a pressure plate. Axial forces appliedby the piston on the clutch pack compress the clutch pack and cause theclutch pack plates to be in frictional contact with each other.Increasing the compression force increases the friction forces betweenadjacent plates. Since one or more of the clutch plates is preventedfrom rotating, compressing the clutch pack applies a braking force tothe axle, and thus to the vehicle.

The piston preferably surrounds the output shaft in a manner that allowsit to apply a relatively even axial force to clutch plates disposedaround the shaft. The piston is movable along the axis of the shaft toapply an axial force to the clutch plates. The piston is preferablyadvanced against the clutch plates by applying a hydraulic force to thepiston. The hydraulic force is preferably applied to the piston using abrake fluid contained in a brake line, with the piston being pushedagainst the clutch pack when a brake pedal is pushed.

The pressure plate also preferably surrounds the output shaft in amanner that allows it to apply a relatively even axial force to clutchplates disposed around the shaft. In contrast to the piston, thepressure plate preferably does not move axially along the shaft, so theforce applied by the pressure plate is in response and substantiallyequal to the force applied by the piston, in much the same way as a wallapplies a force to a person's hand when the person pushes against thewall. Accordingly, when a force is applied to the piston, the pistonmoves toward the pressure plate which, being fixed against axialmovement, pushes back with an equal force (less any frictional forces)to compress a clutch pack positioned between the piston and the pressureplate.

The clutch pack is disposed around the shaft between the piston and thepressure plate. The pack preferably includes two sets of clutch plates.The first set of clutch plates is operably connectable to the outputshaft in a manner effective to cause those clutch plates to rotate withthe output shaft. For example, tabs may be provided on the clutch platesand grooves may be provided on the shaft so that the plate tabs fit inthe shaft grooves and cause the plates to turn when the shaft turns.With this connection, when the output shaft rotates the first set ofclutch plates must rotate as well; and when the first set of clutchplates ceases to rotate so must the shaft.

The second set of clutch plates does not rotate with the shaft, and infact is prevented from rotating. For example, tabs may be provided onthe clutch plates and grooves or indents may be provided on the assemblyhousing, with the plate tabs fitting in the housing grooves/indents toprevent the plates from turning with respect to the housing. With thisconnection, the second set of clutch plates is prevented from rotatingregardless of any rotation of the shaft.

Members of the first, rotating set of clutch plates are interspersedbetween members of the second, fixed set of clutch plates, so that whenthe clutch pack is compressed by axial force applied by the piston andthe pressure plate, the first, rotating set of clutch plates is forcedagainst the second, fixed set of clutch plates. When sufficient force isapplied, the frictional forces between the two sets of clutch platescause the rotating set of plates to slow, and ultimately stop. Thisslows and ultimately stops the rotation of the axle, and applies abraking force to the vehicle.

In another embodiment the inventive braking system includes: a) a portalbox having a stock axle receptacle adapted to receive a stock axle shaftof an off-road vehicle; b) an output shaft operably connectable to astock axle received in the stock axle receptacle of the portal box andeffective to rotate upon rotation of the stock axle; c) ahydraulically-powered piston positioned at a first position along oraround the output shaft and effective for applying an axial force in afirst direction along the axis of the output shaft; and d) a pressureplate positioned at a second position along or around the output shaftand effective for applying an axial force in a second direction oppositethe first direction along the axis of the output shaft in response tothe application of an axial force by the piston; and e) a clutch packpositioned between the pressure plate and the piston, with the clutchpack comprising a first set of clutch plates radially surrounding aportion of the output shaft, and a second set of clutch plates radiallysurrounding a portion of the output shaft. The first set of clutchplates is operably connectable to the output shaft in a manner effectiveto cause those clutch plates to rotate with the output shaft. The secondset of clutch plates does not rotate with the shaft, and in fact isprevented from rotating. Members of the first, rotating set of clutchplates are interspersed between members of the second, fixed set ofclutch plates, so that when the clutch pack is compressed by axial forceapplied by the piston and the pressure plate, the first, rotating set ofclutch plates is forced against the second, fixed set of clutch plates.When sufficient force is applied, the frictional forces between the twosets of clutch plates cause the rotating set of plates to slow, andultimately stop.

The portal box is part of a portal gear lift, and may be originalequipment or an after-market improvement to an all-terrain vehicle or autility task vehicle, such as an ATV or UTV offered by Polaris, Can-Am,Yamaha, Kawasaki, Arctic Cat, Honda, and the like. These portal gearlifts are designed to provide lift to off-road vehicles, while reducinggearing to allow larger tires to be used with good torque.

The portal box preferably has a rear wall that is mountable to mountinghardware, such as a mounting plate, to facilitate mounting the box tothe vehicle suspension. The box also preferably includes one or moresidewalls and a front cover, thus making a sealed compartment to containthe gearing that is preferably used to connect the stock axle (inputshaft) to an output shaft while reducing the gear ratio. An opening forreceiving the stock vehicle axle is provided in the box.

The portal gear lift box preferably includes a linking mechanismeffective for operably connecting the stock axle shaft to the outputshaft. The linking mechanism may comprise one or more gears, which mayinclude an input gear operably linked to the stock axle to rotate uponrotation of the axle, and an output gear operably linked to the outputshaft to rotate the shaft upon rotation of the output gear. When theinput gear has a smaller diameter and number of teeth than the outputgear, a unit rotation of the input gear will cause a smaller rotation ofthe output gear, thus using the gears to reduce the speed of rotation ofthe output shaft relative to the stock axle, and allowing larger tiresto be run without sacrificing torque.

The input gear may be linked to the output gear by a linking gear.Alternatively, a chain or other mechanism may be used to link the inputgear to the output gear. Regardless, the linking mechanism directly orindirectly connects the stock axle to the output shaft in a mannereffective to cause the output shaft to rotate in the same direction asthe stock axle, and preferably at a different, and most preferablyslower, speed.

When the portal gear lift box is installed on a vehicle, the end of thestock axle is received in the housing receptacle of the portal box. Thelinking mechanism links the stock axle to the output shaft. Then, whenpower is applied to turn the stock axle, the linking mechanism transfersthat power from the turning stock axle to the output shaft, thus causingan attached vehicle wheel to turn.

As with the previous embodiment, a piston preferably surrounds theoutput shaft in a manner that allows it to apply a relatively even axialforce to clutch plates disposed around the shaft. The piston is movablealong the axis of the shaft to apply an axial force to the clutchplates. The piston may be advanced against the clutch plates by applyinga hydraulic force to the piston. The hydraulic force is preferablyapplied by a brake fluid contained in a brake line, with the pistonbeing activated by conventional means.

Also as with the previous embodiment, a pressure plate preferablysurrounds the output shaft in a manner that allows it to apply arelatively even axial force to clutch plates disposed around the shaft.The pressure plate preferably does not move axially along the shaft, sothe force applied by the pressure plate is in response and substantiallyequal to the force applied by the piston. When a force is applied to thepiston, the piston moves toward the pressure plate which pushes backwith an equal force (less any frictional forces) to compress a clutchpack positioned between the piston and the pressure plate.

The clutch pack is disposed around the shaft between the piston and thepressure plate, and preferably includes two sets of clutch plates. Thefirst set of clutch plates is connected to the output shaft in a mannereffective to cause those clutch plates to rotate about the axis of theoutput shaft when the output shaft rotates, and the second set of clutchplates is prevented from rotating. Members of the first, rotating set ofclutch plates are interspersed between members of the second, fixed setof clutch plates, so that when the clutch pack is sufficientlycompressed by axial force applied by the piston and the pressure plate,the first set of clutch plates is forced against the second set ofclutch plates and frictional forces between the two sets of clutchplates cause the rotating set of plates to slow, and ultimately stop.

A wheel hub may be mounted to the distal end portion of the outputshaft. The hub is adapted to turn a wheel mounted to said wheel hub uponrotation of the output shaft. Accordingly, when the braking action slowsor stops the rotation of the output shaft, the vehicle slows or stops.

Referring now to the drawings, FIGS. 1 and 2 show one embodiment of thebraking system of the present invention, in partial section. Brakingsystem 100 is provided as part of a portal lift assembly for anall-terrain vehicle or a utility task vehicle (not shown). The systemcomprises a portal box 110 having a stock axle receptacle 111 adapted toreceive a stock axle shaft of an off-road vehicle. A linking mechanism130 is housed in portal box 110 and is effective for linking the stockaxle (not shown) to an output shaft 120. When connect via linkingmechanism 130 to a stock axle, output shaft 120 is rotates upon rotationof the stock axle. Portal box 110 generally includes front housingportion 112, rear housing portion 114 and face plate 116. Front housingportion 112 defines opening 113 through which output shaft 120 passes.Front housing portion 112 also defines a number of grooves 412 asdescribed below. Face plate 116 defines opening 117 through which outputshaft 120 passes. Face plate 116 covers opening 113.

Piston 140 is a caliper piston positioned at a first position along oraround output shaft 120, and is effective for applying an axial force ina first direction along the axis of shaft 120. Piston 140 radiallysurrounds output shaft 120, but preferably does not rotate with it.

A fluid channel 150 is fillable with a non-compressible fluid effectiveto apply a hydraulic force to piston 140 when pressure is applied,thereby moving the piston axially in the first direction along the axisof the shaft. Face plate 116 defines fluid channel 150. A bleeder 400 isincluded to modify the amount and/or pressure of the fluid in the brakeline.

Pressure plate 160 is positioned at a second position along or aroundoutput shaft 120, and is effective for applying an axial force in asecond direction opposite said first direction along the axis of theoutput shaft in response to the application of an axial force in thefirst direction by the piston. Thrust bearing 162 is positioned betweenoutput gear 333 and pressure plate 160 to permit relative rotationbetween output gear 333 and pressure plate 160. In addition, thrustbearing 162 transfers axial forces applied to pressure plate 160 tooutput gear 333. Pressure plate 160 is maintained in a fixed positionthat does not rotate with said output shaft.

A clutch pack 180 is positioned between piston 140 and pressure plate160. Clutch pack 180 comprises a first set of clutch plates 181 radiallysurrounding a portion of shaft 120, and a second set of clutch plates182 radially surrounding a portion of shaft 120. As shown in FIG. 3 ,clutch plates 181 are selectively insertable and removable throughopening 113 over output shaft 120.

The first set of clutch plates 181 is operably connectable to shaft 120in a manner effective to cause those clutch plates to rotate about theaxis of the shaft when the shaft rotates. The second set of clutchplates 182 is prevented from rotating about the axis of the shaft. Thefirst, rotating set of clutch plates 181 are interspersed betweenmembers of the second, fixed set of clutch plates 182, so that when theclutch pack is sufficiently compressed by axial forces applied by piston140 and pressure plate 160, the first, rotating set of clutch plates 181is forced against the second, fixed set of clutch plates 182 so thatfriction forces between members of the first set of clutch plates andmembers of the second set of clutch plates slow and may subsequentlystop the rotation of the shaft.

FIG. 3 is a schematic exploded view of one embodiment of the brakingsystem of the present invention. Portal box 310 has a stock axlereceptacle 311 adapted to receive a stock axle shaft of an off-roadvehicle. A linking mechanism 330 is housed in portal box 310 and iseffective for linking the stock axle (not shown) to an output shaft 320.When connect via linking mechanism 330 to a stock axle, output shaft 320is rotates upon rotation of the stock axle.

Piston 340 is positioned at a first position along or around outputshaft 320, and is effective for applying an axial force in a firstdirection along the axis of shaft 320. A fluid channel 350 is fillablewith a non-compressible fluid effective to apply a hydraulic force topiston 340 when pressure is applied, thereby moving the piston axiallyin the first direction along the axis of the shaft.

Pressure plate 360 is positioned at a second position along or aroundoutput shaft 320, and is effective for applying an axial force in asecond direction opposite said first direction along the axis of theoutput shaft in response to the application of an axial force in thefirst direction by the piston. The pressure plate does not move alongthe axis of the shaft, and does rotate about the axis of the shaft.Instead, the pressure plate remains in a fixed position with respect tothe other assembly components.

A clutch pack 380 is positioned between piston 340 and pressure plate360. Clutch pack 380 comprises a first set of clutch plates 381 radiallysurrounding a portion of shaft 320, and a second set of clutch plates382 radially surrounding a portion of shaft 320.

The first set of clutch plates 381 is operably connectable to shaft 320in a manner effective to cause those clutch plates to rotate about theaxis of the shaft when the shaft rotates. The second set of clutchplates 382 is prevented from rotating about the axis of the shaft. Thefirst, rotating set of clutch plates 381 are interspersed betweenmembers of the second, fixed set of clutch plates 382, so that when theclutch pack is sufficiently compressed by axial forces applied by piston340 and pressure plate 360, the first, rotating set of clutch plates 381is forced against the second, fixed set of clutch plates 382 so thatfriction forces between members of the first set of clutch plates andmembers of the second set of clutch plates slow and may subsequentlystop the rotation of the shaft.

Wheel hub 500 is adapted to receive a distal end portion of output shaft220, and is effective to turn a wheel mounted to the hub upon rotationof the shaft.

Linking mechanism 330 comprises one or more gears. Input gear 331 isoperably linked to the stock axle to rotate upon rotation of the axle.Output gear 333 is operably linked to input gear 331 so that gear 331rotates in the same direction as the stock axle. Linking gear 332connects input gear 331 to output gear 333. The gears are sized suchthat output shaft 320 rotates at a slower speed than the stock axle.

Referring to FIGS. 4-6 , braking system 400 is provided for a portallift assembly for an all-terrain vehicle or a utility task vehicle. Thesystem 400 comprises a portal box 410 having a stock axle receptacle 411adapted to receive a stock axle shaft 600 of an off-road vehicle. Alinking mechanism 430 is housed in portal box 410 and is effective forlinking stock axle 600 to an output shaft. An output shaft 420 isoperably connectable via linking mechanism 430 to stock axle 600, and isadapted to rotate upon rotation of the stock axle. A piston 440 ispositioned at a first position along or around output shaft 420, and iseffective for applying an axial force in a first direction along theaxis of the output shaft. A fluid channel 450 is fillable with anon-compressible fluid, and is effective to apply a hydraulic force topiston 440 when pressure is applied to the fluid, thereby moving thepiston axially along the axis of the shaft.

A pressure plate 460 is positioned at a second position along or aroundoutput shaft 420, and is effective for applying an axial force in asecond direction opposite said first direction along the axis of theoutput shaft in response to the application of an axial force in thefirst direction by the piston.

A clutch pack 480 is positioned between pressure plate 460 and piston440. Clutch pack 480 comprises a first set 481 of clutch plates radiallysurrounding first portions of shaft 420, and a second set 482 of clutchplates radially surrounding second portions of shaft 420. The first set481 of clutch plates is operably connectable to the shaft in a mannereffective to cause those clutch plates to rotate about the axis of theshaft when the shaft rotates. The second set 482 of clutch plates isprevented from rotating about the axis of the shaft. The members of thefirst set 481 of clutch plates are interspersed between members of thesecond set 482 of clutch plates, so that when the clutch pack issufficiently compressed by axial forces applied by said piston and saidpressure plate, the first set of clutch plates is forced against thesecond set of clutch plates so that friction forces between members ofthe first set of clutch plates and members of the second set of clutchplates slow and may subsequently stop the rotation of the shaft.

In the illustrated embodiment the output shaft 420 includes a splinedportion 421 having as multiplicity of teeth 422 and the first set 481 ofclutch plates has a corresponding multiplicity of teeth 483 adapted tomate with the teeth 422 on the splined portion of the output shaft sothat engagement of the splined shaft teeth with the clutch plate teethcauses the first set of clutch plates to rotate with the output shaft.Teeth 422 also engage output gear 333 so that output gear 333 rotateswith output shaft 420. This structure provides a structure forconnecting each of the first set of clutch plates to the shaft in amanner effective to cause those clutch plates to rotate about the axisof the shaft when the shaft rotates.

Similarly, portal box housing includes a set of grooves 412 and thesecond set 482 of clutch plates has a corresponding set of tabs 484adapted to mate with the grooves 412 in the housing so that engagementof the tabs in the grooves prevents the second set of clutch plates fromrotating with respect to the housing.

FIGS. 7 and 8 illustrate preferred embodiments of the first and secondsets of clutch plates. In FIG. 7 , one member of the first set 481 ofclutch plates is illustrated, with plate 481 a having a central opening485 adapted to surround an output shaft. In the illustrated embodimentcentral opening 485 includes a multiplicity of teeth 483 adapted to matewith teeth on a splined portion of the output shaft so that engagementof the splined shaft teeth with the clutch plate teeth causes the firstset of clutch plates to rotate with the output shaft.

In FIG. 8 , one member of the second set 482 of clutch plates isillustrated, with plate 482 a having a central opening 485 adapted tosurround an output shaft. In plate 482 a, central opening 485 is smoothto allow an output shaft to spin freely within opening 485 even when themembers of the first set 481 of clutch plates are engaged with theshaft. The outer surface 490 of plate 482 a includes tabs 484 adapted tomate with the grooves 412 in the housing so that engagement of the tabsin the grooves prevents the second set of clutch plates from rotatingwith respect to the housing.

It is to be appreciated that the description provided herein frequentlyrefers to the piston and/or the pressure plate as applying an axialforce “along” the axis of the shaft. Since these forces are beingapplied by structures (a piston and/or a pressure plate) that preferablysurround the shaft, and that extend radially from the outer surface ofthe shaft, it is to be appreciated that these forces may not be appliedthrough the shaft itself, and by some definitions may therefore notliterally be applied along the axis of the shaft. Therefore, as would berecognized by persons skilled in the art, for the purposes of thisdescription and claims, forces that are applied axially “along the axisof the shaft” would include forces that are applied in a direction thatis substantially parallel to the axis of the shaft, and in relativelyclose proximity to it.

Similarly, the description provided herein frequently refers to thesecond set of clutch plates as being prevented from rotating about theaxis of the shaft. This does not mean that the whole assembly cannot berotated as a unit about the axis of the shaft, although such movementdoes not occur when the assembly is used on a vehicle, and is thereforenot reasonably relevant to a description of the invention. Instead, aswould be recognized by persons skilled in the art, describing the secondset of clutch plates as being prevented from rotating about the axis ofthe shaft means that the second set of clutch plates is prevented fromrotating about the axis of the shaft when the assembly is mounted to avehicle and the entire vehicle is not being rotated. This is typicallyaccomplished by attaching or connecting the second set of plates to thehousing or other structure in some manner such that the second set ofplates does not rotate with respect to the housing.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same are to be considered asillustrative and not restrictive, it being understood that only certainpreferred embodiments have been shown and described and that all changesand modifications that come within the spirit of the invention aredesired to be protected. In addition, it is to be appreciated that thepresent invention may comprise or consist essentially of any or all ofthe described or illustrated features. For example, the presentinvention includes devices and methods comprising any or all of thefeatures described or illustrated in specification or drawings, and thepresent invention includes devices and methods consisting essentially ofany or all of the features illustrated in the specification or drawings.Additionally, any or all of the features and/or embodiments disclosedherein may be combined with any or all of the other features and/orembodiments disclosed herein to provide a device or method thatcomprises or consists essentially of such features.

Finally, the grammatical device “and/or” (such as in “A and/or B”) isused in this disclosure to mean A alone, or B alone, or both A and B.

The invention claimed is:
 1. A braking system for a portal lift assemblyfor an all-terrain vehicle or a utility task vehicle, the systemcomprising: a) a portal box housing having a stock axle receptacleadapted to receive a stock axle shaft of an off-road vehicle, whereinthe portal box housing defines a first opening; b) a linking mechanismhoused in said portal box housing and effective for linking the stockaxle received in the stock axle receptacle to an output shaft, whereinthe linking mechanism comprises an input gear, an output gear, and alinking gear contained in the housing; c) an output shaft operablyconnectable via said linking mechanism to a stock axle received in thestock axle receptacle, and effective to rotate upon rotation of thestock axle, wherein the output shaft extends through the first opening;d) a piston positioned at a first position in the portal box housingalong or around said output shaft and effective for applying an axialforce in a first direction along the axis of the output shaft; e) afluid channel fillable with a non-compressible fluid and effective toapply a hydraulic force to said piston when pressure is applied to fluidin the line, thereby moving the piston axially in said first directionalong the axis of the shaft; f) a pressure plate positioned at a secondposition in the portal box housing along or around said output shaft andeffective for applying an axial force in a second direction oppositesaid first direction along the axis of the output shaft in response tothe application of an axial force in said first direction by saidpiston; g) a clutch pack positioned in the portal box housing betweensaid pressure plate and said piston, said clutch pack comprising a firstset of clutch plates radially surrounding a portion of said shaft, and asecond set of clutch plates radially surrounding a portion of saidshaft, wherein the first set of clutch plates is splined directly to theoutput shaft in a manner effective to cause those clutch plates torotate about the axis of the shaft when the shaft rotates, and whereinthe second set of clutch plates are rotationally coupled to the portalbox housing which prevents the second set of clutch plates from rotatingabout the axis of the shaft, and wherein members of the first set ofclutch plates are interspersed between members of the second set ofclutch plates, so that when the clutch pack is sufficiently compressedby axial forces applied by said piston and said pressure plate, thefirst set of clutch plates is forced against the second set of clutchplates so that friction forces between members of the first set ofclutch plates and members of the second set of clutch plates slow andmay subsequently stop the rotation of the shaft, and wherein the clutchpack is selectively insertable and removable through the first openingover the output shaft.
 2. The braking system according to claim 1wherein the system further includes a wheel hub adapted to receive adistal end portion of said output shaft, and adapted to turn a wheelmounted to said wheel hub upon rotation of the output shaft.
 3. Thebraking system according to claim 2 wherein said input gear is operablylinked to said stock axle to rotate upon rotation of said stock axle,and said output gear is operably linked to said input gear to rotate inthe same direction as said stock axle.
 4. The braking system accordingto claim 1 wherein said linking mechanism directly or indirectlyconnects said stock axle to said output shaft in a manner effective tocause said output shaft to rotate at a slower speed than said stockaxle.
 5. The braking system according to claim 1 wherein said systemfurther includes an end of a stock axle received in said housingreceptacle.
 6. The braking system according to claim 1 wherein saidpressure plate is maintained in a fixed position that does not rotatewith said output shaft.
 7. The braking system according to claim 1wherein said piston radially surrounds said output shaft.
 8. The brakingsystem according to claim 1 wherein said closed fluid channel is thestock brake line of said vehicle.
 9. The braking system according toclaim 1 wherein said output shaft includes a splined portion having asmultiplicity of teeth and the first set of clutch plates has acorresponding multiplicity of teeth adapted to mate with the teeth onthe splined portion of the output shaft so that engagement of thesplined shaft teeth with the clutch plate teeth causes the first set ofclutch plates to rotate with the output shaft.
 10. The braking systemaccording to claim 1 wherein said portal box housing includes a set ofgrooves and the second set of clutch plates has a corresponding set oftabs adapted to mate with the grooves in the housing so that engagementof the tabs in the grooves prevents the second set of clutch plates fromrotating with respect to the housing.
 11. The braking system accordingto claim 2, further comprising a face plate that defines a secondopening, wherein the face plate covers the first opening and wherein theoutput shaft extends through the second opening.
 12. The braking systemaccording to claim 11, wherein removing the face plate and wheel hubprovides access to the first opening such that the clutch pack isselectively removable and insertable through the first opening over theoutput shaft.
 13. The braking system according to claim 11, wherein theface plate defines at least a portion of the fluid channel.
 14. Thebraking system according to claim 1, further comprising a thrust bearingpositioned between the output gear and the pressure plate, wherein thehydraulic force applied to said piston transfers through the clutchpack, the pressure plate and the thrust bearing to the output gear. 15.The braking system according to claim 1, wherein the portal pox housingdefines a groove that extends through the first opening and wherein thesecond set of clutch plates comprise a spline that mates with the grooveto rotationally couple the second set of clutch plates to the housing.16. The braking system according to claim 1, wherein the output shaftcomprises a tooth and wherein the output gear and the first set ofclutch plates are both splined on the tooth.
 17. The braking systemaccording to claim 1, wherein the portal box housing comprised a rearhousing portion and a front housing portion, wherein separating the rearhousing portion from the front housing portion facilitates access to thelinking mechanism, wherein the first opening is in the front housingportion, and wherein the braking system further comprises a face platethat defines a second opening, wherein the face plate covers the firstopening and wherein the output shaft extends through the second opening.18. The braking system according to claim 17, wherein removing the faceplate provides access to the first opening such that the clutch pack isselectively removable and insertable through the first opening over theoutput shaft while the rear housing portion and front housing portionare coupled together.
 19. The braking system according to claim 18,wherein removing the output gear requires separating the rear housingportion from the front housing portion.